The S7 gene and VP7 protein are highly conserved among temporally and geographically distinct American isolates of epizootic hemorrhagic disease virus
Arthropod-borne Animal Diseases Research Laboratory, USDA, ARS, P.O. Box 3965, Laramie, WY 82071, USA.Virus Research (Impact Factor: 2.32). 09/2003; 94(2):129-33. DOI: 10.1016/S0168-1702(03)00166-7
Complete sequences of genome segment 7 (S7) from six isolates of epizootic hemorrhagic disease virus serotype 1 (EHDV-1) and 37 isolates of serotype 2 (EHDV-2) were determined. These isolates were made between 1978 and 2001 from the southeast, mid-Atlantic, Midwest and intermountain United States. Analysis of the S7 sequence similarities showed 98.1% identity among the EHDV-1 isolates and 91.0% identity among the EHDV-2 isolates. Comparison of the deduced amino acid similarities showed an even greater degree of similarity among the isolates (100% among the EHDV-1 isolates and 98.9% identity among the EHDV-2 isolates). There was only 75.8% identity between the EHDV-1 and EHDV-2 isolates at the nucleic acid level; however, there was 93.7% identity between the two groups at the amino acid level. The ratio of non-synonymous to synonymous nucleotide indicates a strong selection for silent substitutions. There was no evidence for reassortment between EHDV-1 and EHDV-2 isolates. The high degree of conservation of S7 gene codons and the VP7 protein, suggests that little variation is allowed in preserving the function of this protein. The high degree of conservation also validates the use of diagnostic tests for EHDV based on S7 and VP7.
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- "Additional studies will be necessary to better understand the ecology of these diseases in a changing environment and climate. Molecular epidemiological investigations of field strains of EHDV and BTV in North America are limited (Pritchard et al. 1995, Cheney et al. 1995, 1996, Wilson et al. 2000, Cheney et al. 2003, Mecham et al. 2003, Murphy et al, 2005, 2006, MacLachlan et al, 2007, Balasuriya et al, 2008, Allison et al, 2010, Anbalagan et al. 2014). Many of these previous studies have relied on partial gene, full gene, or multiple gene segment sequence for analysis and have revealed significant findings regarding novel viruses, outbreak dynamics, and evolution of viruses in North America. "
ABSTRACT: Bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) are arthropod-transmitted viruses in the genus Orbivirus of the family Reoviridae. These viruses infect a variety of domestic and wild ruminant hosts, although the susceptibility to clinical disease associated with BTV or EHDV infection varies greatly among host species, as well as between individuals of the same species. Since their initial detection in North America during the 1950s, these viruses have circulated in endemic and epidemic patterns, with occasional incursions to more northern latitudes. In recent years, changes in the pattern of BTV and EHDV infection and disease have forced the scientific community to revisit some fundamental areas related to the epidemiology of these diseases, specifically in relation to virus–vector–host interactions and environmental factors that have potentially enabled the observed changes. The aim of this review is to identify research and surveillance gaps that obscure our understanding of BT and EHD in North America.
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- "Thus, the most likely explanation is that these animals are in the early stages of infection, when there is circulating virus but no detectable antibody production. An alternative explanation, that the C-ELISA does not detect antibodies in some infected animals due to mutation in the epitope of the VP7 antigen recognised by the monoclonal antibody used to inhibit bovine antibodies in the assay, is possible but unlikely due to the highly conserved nature of this antigen (Mecham et al., 2003). "
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ABSTRACT: In 2006, an exotic reassortant orbivirus, epizootic hemorrhagic disease virus serotype 6 (EHDV-6) [strain (Indiana)], was first detected in the United States. To characterize the reassortment configuration of this virus and to conclusively determine the parental virus of each RNA segment, the complete genome of EHDV-6 (Indiana) was sequenced, in addition to the genomes of representative EHDV-6 and EHDV-2 isolates. Based on genomic comparisons to all other EHDV serotypes, we determined that EHDV-6 (Indiana) originated from a reassortment event between the Australian prototype strain of EHDV-6 (CSIRO 753) and the North American topotype of EHDV-2 (Alberta). Additionally, phylogenetic analysis of all EHDV-6 (Indiana) isolates detected in the United States from 2006 to 2010 suggests that the virus may be undergoing continual reassortment with EHDV-2 (Alberta). In 2010, EHDV-6 (CSIRO 753) was detected in Guadeloupe, demonstrating that the parental virus of the reassortment event is circulating in the Caribbean.